The rapid growth in human population and the changing economic environment are placing ever increasing demand on world water supplies. Because of water scarcity over much of the world, for example, it is important to prepare liquid cleansing products with as little water as possible. Low water cleansing products offer an environmentally friendly cleansing route which lowers strain on water supply. In the current invention, applicants have provided precisely such low water (high soap) cleansers, which are formed by replacing water with a dense liquid crystalline surfactant phase. Quite unpredictably, these formulations are formulated in a manner that, despite being concentrated products, they can be readily dispensed by hand by the end user consumer.
High concentration soap formulations (i.e., formulations in which fatty acid soap comprises >50%, preferably >50 to 80%, more preferably 55 to 80% by wt. and, more preferably, 60 to 80% by wt. of the formulation) typically have a solid or thick gel-like rheology at room temperature. Because of this rheology, such formulations are difficult to pump while in production and are extremely difficult to use as personal cleansers dispensed from a tube, bottle, pump or tottle.
While not wishing to be bound by theory, it is believed that the thick rheology associated with high concentration liquid soap composition is the result of the large amount of hexagonal and solid surfactant phases present in the soap at high concentration.
Unpredictably, applicants have found that if the ratio of free fatty acid to soap (e.g., percent of neutralized soap) in these concentrated soap/free fatty acid liquid soap formulations (e.g., percent of soap neutralized) is maintained within defined critical ranges; and, further, that if (1) concentrations or percentage of soap with specifically defined preferred counterion; (2) preferred percentage of saturation versus unsaturation of fatty acid soap and free fatty acid chain lengths; (3) chain length distribution of fatty acid soap and free fatty acid; (4) amount synthetic surfactant (if any); and (5) concentration of solvent (e.g., water, alkylene, glycol) are all selected and maintained within critically defined parameters, then the amount or degree of hexagonal and solid surfactant phase formation can be controlled such that a highly concentrated liquid soap can be made which has a pumpable viscosity (as specifically defined below). If these parameters are not carefully maintained, on the other hand, the viscosities quickly rise and formulations become difficult or impossible to pump (again, outside of ranges defined by the invention).
It should be noted that when we speak of “pumpable” or “flowable” viscosity, this is a rheological property which can be critical at many different stages in the manufacturing or distribution process. Thus, it can be critical to keep pumpable viscosity for example in the mixing stage of a manufacturing tank; in filing and/or discharging fluid to manufacturing or storage tanks; and/or in filling product into final packaging.
One great benefit of this invention is that the liquids made by this specific selected blend of neutralized soap and unneutralized fatty acids can be made in what would normally be used as a bar production facility. Unexpectedly, and unpredictably, applicants have found that the blends of fatty acid and soap used in the bar production process can be used to produce concentrated liquids as well (i.e., assuming the criticalities noted above are maintained).
In addition, concentrated liquids having the correct rheology and which are produced by the process of the invention can be sold as a “concentrated liquid product” whereby the consumer can be instructed to dilute the product at home (resulting in both environmentally friendly packaging and tremendous cost savings); or the concentrated liquid can be transported to a different place and later diluted as part of the production process. In the latter case, this allows the producer to produce more cheaply than when normally making liquid soap/syndet composition (e.g., reduction in transportation costs due to use of concentrates rather than transporting heavy water-containing product). As indicated above, tremendous efficiencies between bars and liquids are also found because any excess capacity from bar manufacturing sites may be used to make liquids.
The key, as noted above, is to obtain a final concentrated liquid formulation in which variables such as (1) ratio of neutralized soap to unneutralized fatty acid; (2) counterion; (3) chain length of fatty acid soaps and free fatty acids; (4) synthetic surfactant, if any; (5) and solvent are critically controlled to obtain viscosities below a defined level and defined by a dispensing force needed to dispense the product. This goal in turn may be achieved either by controlled neutralization of fatty acid; or by using mixtures of free fatty acid and fully neutralized soap such that resulting formulation falls within defined formulation parameters where this defined pumpable or squeezable rheology is obtained.
It should be noted that there is interplay between variables and these variables can be adjusted as long as the overall goal of maintaining a low dispensing force is maintained. Thus, for example, the degree of neutralization or exact percent of long chain or low chain length soap/fatty acids may be closer to the upper or lower ranges in which case adjustments can be made to solvent level or level or synthetic surfactant.
In one embodiment of the invention, for example, there may be present only soap/fatty acid and neutralizing solvent such as potassium hydroxide (e.g., no viscosity reducing co-solvent such as dipropylene glycol, propylene glycol). Such embodiment would minimize the level of long chain length, fatty acid/soaps (which tend to increase viscosity) and certainly ensure their level is within defined ranges. In another embodiment of the invention, the concentrate could tolerate higher levels of longer chain length soaps/fatty acids but would also have some required level of synthetic surfactant and/or viscosity reducing co-solvent to ensure the dispensing force is within defined parameters. This second embodiment is specifically claimed in a co-pending application filed on the same date by applicants.
As far as applicants are aware, the art does not disclose the specific parameters required to obtain concentrated soap liquids of the invention, or a method of obtaining these liquids such that the liquid soap has a pumpable, readily pourable rheology, i.e., measured by dispensing force which is defined in the protocol. Specifically, there is nothing in the art which would teach or suggest the person of ordinary skill either that this is a problem or how to begin to solve such problem.
GB 699 189 is an example of references disclosing compositions made by neutralization of fatty acids with caustic potash. Although the fatty acids of the resulting liquid cleansers are neutralized, there is no indication of partial neutralization, or of the resulting critical, specific ratios, of fatty acid to soap. Further, there is no disclosure that such specific ratios, or of any of the other criticalities of saturation, chain length, etc. which are required to obtain the pumpable (e.g., squeezable), concentrated soap liquids of the invention having defined viscosity. This reference is typical of many older references from before 1960.
More recent references include those which use soap at much lower levels. Examples of such references include WO 95/13355, WO 05/18760 and WO 97/27279.
U.S. Pat. Nos. 5,952,286 and 6,077,816, both to Puwada, relate to the use of free fatty acid to form lamellar structures in liquid cleansing products having 9 to 50% surfactant concentration. Overall concentrations of surfactant in these references are lower than the overall concentration of surfactant (e.g., soap plus fatty acid) of the compositions of the invention and the concentrations of water are higher than those of our invention. Further, there is no recognition of use of specific ratios of fatty acid to soap or of other criticalities noted.
U.S. Pat. No. 7,351,749 to Divone et al. relates to the process for manufacture of personal care products using concentrated water phase. The reference is not related to concentrated soaps or to specific ratios of fatty acid to the soap.
U.S. Pat. Nos. 5,296,158 and 5,149,574 to MacGilp disclose compositions with potassium soap and free fatty acid. Concentrations of water are 55-90% compared to top solvent concentration (water/solvent) of 40% in our invention. U.S. Pat. No. 4,310,433 to Stiros discloses mixtures of neutralized and unneutralized fatty acids where fatty acids are mixtures of saturated and unsaturated. The compositions again comprise 50-95% water, levels of solvent well above those of our invention. Various other references to MacGilp, (U.S. Pat. No. 5,158,699; U.S. Pat. No. 5,296,157) also have much higher levels of water/overall solvent.
U.S. Pat. No. 5,308,526 to Dias discloses composition with K+ soap and free fatty acids. They comprise 35-70% water. The compositions have much less than 50% soap.
WO 2004/080431 to Unilever relates to method of preparing personal care compositions from concentrate. There appears to be no recognition of a concentrate having critically specific levels of neutralization (ratio of fatty acid to soap) or other noted variables which provide a rheology allowing concentrated soap formulations to be pumped or readily dispensed. The reference also fails to disclose a separate concentrated liquid (e.g., as separate stand alone product) which can be sold to consumers for possible dilution at home.
GB 2005297 (Unilever) discloses liquid soap compositions comprising potassium soap, 0-20% glycerol, 5-20% alkylene glycol, 0-10% free fatty acids and 20-50% water. Levels of soap are well below the 50% level of the subject invention.
GB1427341 (Unilever) discloses potassium soap crystals in aqueous glycerin solution comprising 12-40% glycerol and 20-50% H2O. Again, levels of soap are well below those of compositions of the invention.
JP 2006/282,591 and JP 2002/226,359 relate to face wash creams. Neither appears to disclose criticality of fatty acid to soap in combination with other criticalities to yield a high concentrated, pumpable liquid soap.
None of the reference discloses high soap (>50% by wt.) compositions having a critical ratio of fatty acid to soap or combination with criticalities of saturation, chain length, solvent etc. to produce pumpable, concentrated liquid soaps. There also is no reference relating to sale of such specific compositions as stand alone concentrates with instructions for home dilution.